只需将变量声明为public即可

public int variable1;
  public int variable2;

  Class1() {
    this.variable1 = 400;
    this.variable2 = 600;
  }

Class1 obj = new Class1();
obj.variable1();

或者将它们设置为私有并添加getter

 private int variable1;
  private int variable2;

  Class1() {
    this.variable1 = 400;
    this.variable2 = 600;
  }

  public int getVariable1() {
     return this.variable1;
  }

  public int getVariable2() {
     return this.variable2;
  }

然后

Class1 obj = new Class1();
obj.getVariable1()

您必须返回该变量，如下所示:

class Class1 {
    public int A() {
        int a = 5 + 6;
        return a;
    }
}

您需要添加这样的返回语句:return a； 在（）函数的末尾返回值